This invention relates to diagnostic testing of a hydrostatic transmission, and in particular, to an automated diagnostic system that can run tests that would normally be conducted manually by a technician.
Diagnosing problems in a hydrostatic transmission can be a tedious and ambiguous task. In order to ascertain if particular components are functioning properly, a technician typically installs a variety of pressure or flow gauges, taps into the electrical circuits, and then follows testing procedures. The testing procedures include making notes and performing calculations to try to ascertain that the individual components are functioning properly. Such tests can also be subjective and highly dependent upon the skills and dedication of the technician to following procedures.
Another problem with current testing techniques is that, as the technician may be uncertain as to the real cause of a problem, a parts-swapping approach may be taken to pick and choose parts to replace until the appropriate nonfunctioning part is removed. This type of approach can significantly increase warranty costs as non-defective parts may be replaced.
Accordingly, it is an object of the present invention to automate diagnostics of transmission hydraulic components. It is a further object of the invention to allow a technician to select customer complaints from an existing monitor so that the monitor can instruct the technician to relocate existing pressure transducers already on the crawler and to do a “run test” on the monitor.
It is another object of the present invention to drive appropriate electrical signals to control the transmission hydraulic components while the microprocessor reads resulting speeds and pressures. A further object of the invention is that the microprocessor can perform calculations on the results, determine the hydraulic problem, and provide feedback to the technician on adjustments for part replacements that need to be made.
Additionally, it is a goal that the hydraulic test system not require any testing devices beyond those currently existing on the crawler. This eliminates the need for coordinating separate laptops or diagnostic tools or boxes. In addition, as the method is designed to use an on-board transmission microprocessor, test data are embedded in the crawler itself, which eliminates confusion about which test results or values apply to the specific model. The subject invention should avoid the need to consult a service manual and eliminate mistakes inherent with such a procedure.
It is believed that such hydraulic test procedures will significantly reduce the time required to perform a test. Also, the testing process should be more repeatable and valid by removing subjectivity from the results. One way to accomplish this is using the on-board microprocessor to electronically simulate a technician moving levers and changing speeds as required with current tests.
An additional object of the invention is to allow the automated tests to factor in other factors to the test results. For example, temperature could be continuously monitored and factored into the test results while the test is being conducted. It is believed that more parameters are available to be monitored by the microprocessors than can be monitored by a technician using pressure gauges and voltmeters.